我的自定义 DbExecutionStrategy 没有被调用-C#/.NET问题

My custom DbExecutionStrategy is not being called(我的自定义 DbExecutionStrategy 没有被调用)

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问题描述

我最初的问题是我在更新我的 SQL 数据库时经常遇到死锁.通过一些研究，我发现我能够定义一个自定义 DbConfiguration 和一个 DbExecutionStrategy，它指示实体框架在 x 毫秒和 y 次后出现某些错误后自动重试.太好了！

My original problem was that I was experiencing deadlocks often when updating my SQL database. Through a little bit of research, I found that I'm able to define a custom DbConfiguration and with it a DbExecutionStrategy which instructs Entity Framework to automatically retry after getting certain errors after x milliseconds and y number of times. Great!

因此，请遵循 https://msdn.microsoft.com/en- 上的指南us/data/jj680699，我构建了我的自定义 DbConfiguration，正在使用，但关联的 DbExecutionStrategy 似乎被忽略了.

So, following the guide at https://msdn.microsoft.com/en-us/data/jj680699, I build my custom DbConfiguration, which is being used, but the associated DbExecutionStrategy seems to be ignored.

最初，我的整个 DbConfiguration 都被忽略了，但我发现这是因为我在 app.config 中引用了它，并使用 DbConfigurationType 属性 [DbConfigurationType(typeof(MyConfiguration))] 装饰了我的实体构造函数.现在我只使用了 app.config，至少我的自定义配置正在被调用.

Originally, my entire DbConfiguration was being ignored, but I found that was because I was referencing it in my app.config as well as decorating my entity constructor with the DbConfigurationType attribute [DbConfigurationType(typeof(MyConfiguration))]. Now that I'm only using the app.config, at least my custom configuration is being called.

在最简单的形式中，我的自定义配置如下所示:

In its simplest form, my custom config looks like this:

public class MyConfiguration : DbConfiguration
{
    public MyConfiguration()
    {
        System.Windows.MessageBox.Show("Hey! Here I am!"); //I threw this in just to check that I was calling the constructor. Simple breakpoints don't seem to work here.
        SetExecutionStrategy("System.Data.SqlClient", () => new MyExecutionStrategy(3, TimeSpan.FromMilliseconds(500)));
    }
}

我的自定义 DbConfiguration 在我的 app.config 中被引用，如下所示:

My custom DbConfiguration is referenced in my app.config like so:

<entityFramework codeConfigurationType="MyDataLayer.MyConfiguration, MyDataLayer">
    ...
</entityFramework>

我的自定义 DbExecutionStrategy 是这样构建的:

My custom DbExecutionStrategy is built like so:

private class MyExecutionStrategy : DbExecutionStrategy
{
    public MyExecutionStrategy() : this(3, TimeSpan.FromSeconds(2))
    {
        System.Windows.MessageBox.Show($"MyExecutionStrategy instantiated through default constructor.");
    }

    public MyExecutionStrategy(int maxRetryCount, TimeSpan maxDelay) : base(maxRetryCount, maxDelay)
    {
        System.Windows.MessageBox.Show($"MyExecutionStrategy instantiated through parametered constructor.");
    }

    protected override bool ShouldRetryOn(Exception ex)
    {
        System.Windows.MessageBox.Show($"Overriding ShouldRetryOn.");

        bool retry = false;

        SqlException sqlException = GetSqlException(ex);

        if (sqlException != null)
        {
            int[] errorsToRetry =
            {
                1205,  //Deadlock
                -2     //Timeout
            };

            if (sqlException.Errors.Cast<SqlError>().Any(x => errorsToRetry.Contains(x.Number)))
            {
                retry = true;
            }
        }

        if (ex is TimeoutException)
        {
            retry = true;
        }

        return retry;
    }
}

我在这段特定的代码中根本没有遇到任何问题.

I'm not hitting anything at all in this particular piece of the code.

可能需要注意的一点是，到目前为止我看到的每个示例(例如 http://blog.analystcircle.com/2015/08/01/connection-resiliency-in-entity-framework-6-0-and-above/) 已使用

One thing that may be of note, is that every example I've seen so far (for example http://blog.analystcircle.com/2015/08/01/connection-resiliency-in-entity-framework-6-0-and-above/) has casted the exception in ShouldRetryOn directly to a SqlException using

SqlException sqlException = ex as SqlException;

我发现使用这种方法总是会导致 null SqlException，因为我的程序抛出了一个无法转换为 SqlException 的 EntityException.我的底层SqlException其实就是EntityException内部异常的内部异常.所以，我整理了一个简短的递归调用来挖掘并找到它.

I found that using this method always resulted in a null SqlException because my program is throwing an EntityException which can't be cast into a SqlException. My underlying SqlException is actually the inner exception of the inner exception of the EntityException. So, I put together a short recursive call to dig in and find it.

private SqlException GetSqlException(Exception ex)
{
    SqlException result = ex as SqlException;

    if (result == null && ex.InnerException != null)
        result = GetSqlException(ex.InnerException);

    return result;
}

这可以正常工作，但是当我找到的示例不存在时，我需要这样做，这可能是出问题的线索.EntityExceptions 不会触发 DbExecutionStrategy 吗?如果不是，为什么这被列为与 EF 6 一起使用的解决方案?任何见解将不胜感激.

This works properly, but the fact that I need to do it when the examples I've found don't is probably a clue as to what's going wrong. Do EntityExceptions not trigger a DbExecutionStrategy? If not, why is this listed as a solution to be used with EF 6? Any insight would be much appreciated.

进一步挖掘 DbExecutionStrategy 的源代码 (https://github.com/aspnet/EntityFramework6/blob/master/src/EntityFramework/Infrastructure/DbExecutionStrategy.cs)，我发现从EntityException中找到我的SqlException的递归函数是不必要的.DbExecutionStrategy 有一个函数 UnwrapAndHandleException，它就是这样做的，并将 SqlException 传递给 ShouldRetryOn.所以，看来我又回到了第一格.

Doing some more digging into the source for DbExecutionStrategy (https://github.com/aspnet/EntityFramework6/blob/master/src/EntityFramework/Infrastructure/DbExecutionStrategy.cs), I've found that my recursive function to find my SqlException from the EntityException is unnecessary. DbExecutionStrategy has a function UnwrapAndHandleException which does just that and passes the SqlException on to ShouldRetryOn. So, it seems I'm right back at square one.

编辑 2:不是真正的解决方案，因为它没有解释为什么我的 DbExecutionStrategy 没有按应有的方式被调用，但我发现如果我明确调用执行策略，它就可以工作.

EDIT 2: Not really a solution, because it doesn't explain why my DbExecutionStrategy isn't being called as it should, but I have found that if I explicitly call the execution strategy, it works.

明确使用执行策略的代码是:

The code to use the execution strategy explicitly is:

var executionStrategy = new MyConfiguration.MyExecutionStrategy();

executionStrategy.Execute(
    () =>
    {
        //build your context and execute db functions here
        using (var context = new Entities())
        {
            ...do stuff
        }
    });

我的自定义 DbExecutionStrategy 没有被调用

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